Heat exchanger including fluid lines encased in aluminum

ABSTRACT

Heat exchange apparatuses configured for various applications so as to transfer heat to or from a fluid to be heated or cooled, respectively. The heat exchange apparatus includes at least one fluid line for containing the product fluid to be heated or cooled. The line includes an inlet into which the fluid is introduced, as well as an outlet at an opposite end of the line through which the fluid exits. The heat exchange apparatus also advantageously includes a cast metallic body which encases at least a portion of the fluid tube.

RELATED APPLICATIONS

The present application claims the benefit of U.S. Patent Application Ser. No. 60/978,844, filed Oct. 10, 2007, entitled “HEAT EXCHANGER INCLUDING FLUID LINES ENCASED IN ALUMINUM”, the disclosure of which is incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

1. The Field of the Invention

The present invention is in the field of heat exchangers used to transfer heat to or from a fluid (e.g., a liquid or gas).

2. The Relevant Technology

Heat exchangers are used in various applications to transfer heat to or from fluid to be heated or cooled, respectively. For example, in a conventional vehicle radiator hot coolant (e.g., antifreeze) is passed through the radiator block to cool the coolant prior to recycling the coolant back into the engine so as to draw heat away from the engine. Such a typical radiator includes a block of narrow internal and outside diameter tubing formed of steel through which the coolant is passed. The exterior surface of the tubing typically includes delicate fins formed thereon so as to increase convective heat transfer to surrounding air. As the air passes along the exterior surface of the tubing and fins, heat is drawn away from the hot coolant within the tubing. In other words, the radiator relies on air convection cooling in order to cool the hot coolant.

In another example, in a typical gas water heater, a gas burner is located at the bottom of the tank. Heat from the gas burner is used to heat water within the insulated tank. Hot exhaust gases from the burner may be passed through a flue pipe running through the center of the tank in order to use heat within the hot exhaust gases to more efficiently heat the water within the tank. In an electric water heater, an electrical resistance heating element is located within the water tank (i.e., in direct contact with the water) so as to heat the water within the tank.

Although existing heat transfer systems are generally adequate in providing heating and/or cooling to a fluid, the fins of existing vehicle radiators and similar heat exchangers are easily damaged, such systems are often highly variable (e.g., it can be difficult to maintain a relatively constant engine temperature), and heat transfer is often relatively inefficient. It would be an improvement in the art to provide heat exchange systems capable of providing heating and/or cooling with greater efficiency at lower cost. It would be a further advantage if such a system were relatively simple to manufacture, install, and operate.

BRIEF SUMMARY OF THE PREFFERED EMBODIMENTS

The present invention relates to heat exchange apparatuses configured for various applications so as to transfer heat to or from a fluid to be heated or cooled, respectively. As used herein, the term “fluid” may include liquids, gases (e.g., air), and/or other materials that are flowable (e.g., even a slurry including solids) and/or mixtures thereof. The inventive heat exchange apparatus includes at least one tube for containing the product fluid to be heated or cooled. The tube includes an inlet into which the fluid is introduced, as well as an outlet at an opposite end of the tube through which the fluid exits. The heat exchange apparatus also advantageously includes a cast metallic body which encases at least a portion of the fluid tube. In one embodiment an additional tube for conveying a heating or cooling fluid may also be encased within the cast metallic body, and the tubes may be arranged according to various configurations so as to promote heat transfer to or from the product fluid tube, as desired.

The cast metallic body advantageously comprises aluminum or an aluminum alloy, and encases at least part of a central portion of the fluid tube, the central portion being defined as the portion of the tube between the tube inlet and the tube outlet. In addition to the product fluid tube configured to convey the fluid to be heated or cooled, the apparatus may further include a separate tube for conveying a heating or cooling fluid (e.g. a refrigerant) for more efficient heat transfer. As an alternative to a tube for conveying a heating fluid, the apparatus may include an electrical resistance heating coil. The second tube or heating coil is disposed in close proximity to the fluid product tube, and is also encased within the cast metallic body so that the two fluid tubes are in heat exchange relationship with one another.

Heat exchange relationship is defined as a spatial configuration such that heat can flow between the at least one fluid tube and the at least one heating/cooling tube or heating coil. For example, the two tubes and/or the fluid tube and heating coil may be arranged in a substantially countercurrent flow relationship. Preferably, the second tube or heating coil is spaced apart from the fluid product tube so that the metallic body encases and fully surrounds the tubes. Such a configuration in which the metallic body is disposed between the fluid product tube and the second tube/heating coil provides for improved heat transfer to or from the fluid within the fluid product tube as a result of specific properties attributable to the aluminum cast metallic body.

These and other advantages and features of the present invention will become more fully apparent from the following description and appended claims, or may be learned by the practice of the invention as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

To further clarify the above and other advantages and features of the present invention, a more particular description of the invention will be rendered by references to specific embodiments thereof, which are illustrated in the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. The invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:

FIG. 1 is a perspective view of an exemplary gas water heater including a metallic cast plate heating block within which a fluid line is encased;

FIG. 2A is a perspective view of an exemplary heat exchanger device including a product fluid tube having an inlet and outlet, and metallic body which encases a central portion of the product fluid tube between the inlet and outlet;

FIG. 2B is a phantom view of the device of FIG. 2A, showing the encased central portion of the product fluid tube;

FIG. 3A is a perspective view of an alternative heat exchanger device similar to that of FIG. 2A, but further including convection cooling slots formed within the metallic body through which air may pass from one side of the device to the other;

FIG. 3B is a partial phantom view of the device of FIG. 3A, showing the encased central portion of the product fluid tube and the convection cooling slots which are formed through the cast metallic encasing body;

FIG. 4A is a perspective view of another exemplary heat exchanger device including a product fluid tube having an inlet and outlet, an additional heating/cooling fluid tube, and metallic body which encases a central portion of both the product fluid tube and the heating/cooling tube between the inlet and outlet;

FIG. 4B is a phantom view of the device of FIG. 4A, showing the encased central portions and routing of the product fluid tube and the additional heating/cooling fluid tube;

FIG. 4C is a close up phantom view of an alternative device similar to that of FIG. 4A, but including an accumulator near an inlet end of the heating/cooling fluid tube;

FIG. 5A is a perspective view of an exemplary heat exchanger system including a heat exchanger device similar to that illustrated in FIG. 4A, including a product fluid tube as well as a cooling fluid tube encased within the cast metallic body. The heat exchanger system further includes a secondary cast metallic body for condensing warm cooling fluid;

FIG. 5B is a phantom view of the system of FIG. 5A, showing the encased central portions and routing of the product fluid tube and cooling fluid tube;

FIG. 5C is a close up phantom view of the secondary cast metallic body;

FIG. 6A is a perspective view of an alternative secondary cast metallic body that may be used with a system similar to that of FIG. 5A; and

FIG. 6B is a phantom view of the secondary cast metallic body of FIG. 6A showing the encased central portions and routing of the cooling fluid tube.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS I. Introduction

The present invention relates to heat exchange apparatuses configured for various applications so as to transfer heat to or from a fluid to be heated or cooled, respectively. The inventive heat exchange apparatus includes at least one tube for containing the product fluid to be heated or cooled. The tube includes an inlet into which the fluid is introduced, as well as an outlet at an opposite end of the tube through which the fluid exits. The heat exchange apparatus also advantageously includes a cast metallic body which encases at least a portion of the fluid tube. The inventor has found that providing a cast aluminum body that surrounds the product fluid tube greatly improves heat transfer to or from the fluid contained within the tube relative to a system not including such a casting (e.g., a system in which the full length of the exterior of the tube is exposed to air rather than aluminum).

II. Exemplary Heat Exchanger Apparatuses

FIG. 1 illustrates an exemplary gas water heater apparatus 100 including a water tank 102, a cold water inlet 104, a hot water outlet 106, a gas burner 108, and a heat exchange block 110. Block 110 includes a water tube 112 having an inlet end 114 and an outlet end 116. A central portion of tube 112 is encased within cast metallic body 118. Cold water enters tube 112 through inlet 114 and is conveyed to a central portion of tube 112 which is encased by metallic (e.g., aluminum) casting 118. Heat from burner 108 heats casting 118, and the heat is in turn transferred through casting 118 to tube 112 and the cold water contained therein so as to heat the water. Hot water exits block 110 from outlet 114 into water tank 102. The heated water is stored within tank 102 until needed, at which time it is drawn out of tank 102 through hot water outlet 106. In one embodiment inlet 104 may be connected to block inlet 114 so that water entering heater apparatus 100 is first fed through block 110 where it is heated. The water may then be introduced into tank 102. In another embodiment, water may enter tank 102 from inlet 104, and then be drawn from tank 102 into inlet 114 and through block 110, where it is heated. Water may then be deposited into tank 102. Alternatively, an electrically resistive heating coil may replace tube 112. Of course, it may be helpful to electrically isolate such a heating coil from the encasing block 110 (e.g., through an electrically insulative layer around the heating coil).

Although the reasons for the improved heat transfer are not completely understood, it is believed that the thermal conductivity and possibly other physical properties (e.g., heat capacity) of the aluminum of block 110 play a key role. In any case, it has been found that encasing the fluid lines in a metal comprising aluminum (e.g., at least about 50% by weight aluminum, more preferably at least about 75% by weight aluminum, more preferably at least about 90% by weight aluminum, and even more preferably the encasing metal consists essentially of aluminum) results in significantly faster and more effective transfer of heat either to or from the product fluid to be heated or cooled. In addition, the encased designs of the present invention are robust, as opposed to typically fragile, intricate designs in which tubes are attached to heat transfer fins, which designs depend heavily on convention heat transfer (e.g., typically used in vehicle radiator and other heat exchanger designs).

FIGS. 2A and 2B illustrate another heat exchange apparatus 200. A product fluid line (i.e., tube) 212 includes an inlet 214 and an outlet 216. A central portion of fluid line 212 is encased within metallic cast body 218, as illustrated.

FIGS. 3A and 3B illustrate another exemplary heat exchange apparatus 300 which may be configured as a vehicle radiator, for example. A product fluid tube or line 312 includes an inlet 314 and an outlet 316. A central portion of fluid line 312 is encased within metallic cast body 318, similar to the embodiment illustrated in conjunction with FIGS. 2A and 2B. By contrast, apparatus 300 further includes convection cooling slots 320 formed within cast body 318. Slots 320 are formed so as to pass completely through body 318 from one side thereof to the other. Air or another cooling fluid (in other conceivable applications a heating fluid may be used) is able to pass through slots 320 so as to increase the speed and efficiency of heat transfer as a result of convection. For example, in a conventional vehicle radiator hot coolant (e.g., antifreeze) may be passed through a radiator block similar to device 300 to cool the coolant prior to recycling the coolant back into the engine so as to draw heat away from the engine. Such an apparatus may advantageously not include delicate fins attached to fluid line 312 as in a conventional radiator, and still achieve comparable if not improved heat transfer as a result of the encasing 318 formed of e.g., aluminum that surrounds at least a portion of fluid line 312. Of course it may be possible to include more than one product tube routed independently (i.e., not in fluid communication with another product tube) through encasing block 318.

The cast metallic body preferably comprises aluminum or an aluminum alloy, and encases at least part of a central portion of the fluid tube, the central portion being defined as the portion of the tube between the tube inlet and the tube outlet. Preferably, the cast metallic body encases as much of the central portion of the fluid tube as possible. As illustrated, substantially all of the central portion may be encased. In addition to the product fluid tube configured to convey the fluid to be heated or cooled, the apparatus may further include a separate tube for conveying a heating or cooling fluid (e.g., a refrigerant such as FREON or another fluorocarbon refrigerant) for more efficient heat transfer. FREON coolants are one particularly preferred class of gaseous cooling fluids. Liquids may alternatively be used (e.g., ethylene glycol and/or water), although the gaseous fluorocarbon coolants are preferred.

FIGS. 4A-4B illustrate one such exemplary heat exchange apparatus 400. A product fluid tube or line 412 includes an inlet 414 and an outlet 416. A central portion of fluid line 412 is encased within metallic cast body 418, similar to the embodiment illustrated in conjunction with FIGS. 2A and 2B. By contrast, apparatus 400 further includes an additional tube 412′ for conveying a heating or cooling fluid in close proximity and in heat exchange relationship to tube 412 through encasing portion 418. As shown in FIG. 4B, the product fluid tube 412 may be configured so that the product fluid is conveyed in a direction that is substantially parallel to one axis of rectangular encasing casting 418 (i.e., most of the length of tube 412 runs parallel to a longitudinal axis A of casting 418). In one embodiment, at least about 50% of the length of tube 412 runs substantially parallel to axis A, more preferably at least about 60% of the length of tube 412 runs substantially parallel to axis A, and most preferably at least about 70% of the length of tube 412 runs substantially parallel to axis A.

In addition, to increase the length of tube 412 encased within casting 418 while also minimizing the volume of casting 418, tube 412 may be coiled within encasing portion 418, as seen in FIG. 4B. For example, illustrated tube 412 includes 5 portions extending substantially the full length of encasing portion 418 so that tube 412 is at least about 5 times longer than the length dimension of encasing 418 that lies parallel to axis A. Similarly, tube 412′ is configured to run substantially parallel to another axis of rectangular casting 418 (i.e., most of the length of tube 412′ runs parallel to transverse axis B which is substantially perpendicular to axis A). In addition, to increase the length of tube 412′ encased within casting 418 while also minimizing the volume of casting 418, tube 412′ may be coiled within encasing portion 418, as seen in FIG. 4B. For example, illustrated tube 412′ includes 4 portions extending substantially the full width of encasing portion 418 so that tube 412′ is at least about 4 times longer than the width dimension of encasing 418 that lies parallel to axis B. Of course, the routing of tube 412′ may be more similar to that of tube 412, only turned 90°. Such a configuration would align tube 412′ so as to run in a direction that is substantially parallel to the other axis of rectangular encasing casting 418.

Because tube 412′ also includes substantial portions (e.g., about 50%) which are oriented substantially parallel to axis A, illustrated tube 412′ is more typically at least about 5 or even 8 times longer than the width dimension of encasing portion 418. In one embodiment, the lengths of encased portions of tubes 412 and 412′ are substantially equal. The two tubes 412 and 412′ are arranged in heat exchange relationship so that heat can flow between product fluid tube 412 and the heating/cooling tube 412′. In the illustrated embodiment, the tubes are arranged so that substantial portions of the tubes are arranged in a perpendicular flow relationship (i.e., a majority of the length of tube 412 runs parallel to axis A, and a majority of tube 412′ may run parallel to axis B).

In another example, the two tubes may be arranged in a substantially countercurrent flow relationship in which the tubes are coiled along the same general path, and wherein one tube is configured so that the inlet end coincides with the outlet end of the other tube. For example, the routing of tube 412′ may be more similar to that of tube 412, only turned 1800. Tubes 412 and 412′ are spaced apart so that the metallic body 418 encases the tubes. Such a configuration in which the metallic body is disposed between the fluid product tube 412 and the cooling/heating tube 412′ provides for improved heat transfer to or from the fluid within the fluid product tube 412′.

The fluid lines of the heat exchange device may be formed of any suitable material (e.g., a metal). Metal materials may be preferred over other materials (e.g., plastics) because of the thermal insulative as opposed to conductive properties of such plastic materials. In one embodiment, they are formed of stainless steel. Although preferred embodiments may include a fluid line configured as a tube, other shapes and configurations may alternatively be used. In one embodiment, one or more of the fluid lines may include a portion formed so as to define an accumulator portion 413′ where the fluid may accumulate. In one particular embodiment, the additional tube (e.g., tube 412′) for conveying a heating or cooling fluid in close proximity and in heat exchange relationship to the product fluid tube includes such an accumulator. Such an accumulator may comprise a portion of the tube that is formed so as to have a greater internal diameter than an adjacent portion of the tube. The accumulator may be formed in a portion of the tube which is inclined relative to a horizontal “floor” surface so as to cause the fluid to drain downward by force of gravity. Such an accumulator may either be encased within the encasing casting (e.g., 418), or alternatively formed outside the boundaries of the encasing casting. An example of such an accumulator that may form a portion of any of the described heat exchange devices is shown in FIG. 4C.

Typically, coolant exiting from line 416′ may be sent to a condenser, and then to a compressor before being recycled back in through inlet 414′. FIG. 5A illustrates a heat exchanger system 500 that includes a secondary metallic encasing body so as to eliminate the need for such a condenser. System 500 includes a product fluid tube or line 512 having an inlet 514 and an outlet 516. A central portion of fluid line 512 is encased within metallic cast body 518. System 500 also includes a heating/cooling fluid line 512′ for conveying a heating or cooling fluid in close proximity and in heat exchange relationship to tube 512 through encasing portion 518. In addition, encasing body 518 is illustrated similar to the embodiment illustrated in conjunction with FIGS. 3A and 3B so as to include through slots 520 for convection cooling.

System 500 also includes a secondary metallic encasing body 518′, which advantageously eliminates the need for a condenser (a condenser in the case of a cooling fluid passing through heating/cooling tube 512′). In heating systems, a similar configuration may allow elimination of a heater. Cooling fluid exits encasing body 518 through outlet 516′. The temperature of the fluid therein is warmer than it was upon entering through inlet 514′ as a result of heat transfer within the block 518 from product line 512 (which is cooled). In order to recycle the cooling fluid (e.g., FREON), the cooling fluid must be cooled or “condensed”.

Secondary block 518′ and associated structure as shown in FIGS. 5A-5C serve this function. This portion of cooling fluid tube 512″ enters secondary block 518′ (e.g., in the shape of a cylinder with a central through-hole slot 520′), finally exiting secondary block 518′ at outlet 516″. Metallic body 518′ is surrounded by a housing 522 which is advantageously spaced apart (i.e., space 524) from body 518′. The illustrated embodiment further includes a relatively small fan 526 at one end of body 518, which pulls air through both central hole 520′ as well as through space 524, providing forced convention against body exterior cylindrical surfaces of secondary metallic body 518′. Although illustrated as square, housing 522 may take other shapes (e.g., cylindrical so as to provide for concentric cylinders in which body 518′ is a central cylinder and housing 522 is an outer cylinder with a space 524 there between). Cooled/condensed coolant fluid exiting secondary block 518′ at outlet 516″ may be sent to a compressor and then recycled to inlet 514′.

Such a secondary block eliminates the need for a traditional condenser, and accomplishes cooling/condensation according to principles of the present invention through use of a metallic encasing member, which provides excellent efficiency at low cost. For example, the secondary block, housing, and fan may have an area of about 5 inches by 5 inches (i.e., fan 526 measures about 5 inches on each side). Such a sized apparatus has been found to provide the same cooling/condensation as a traditional condenser and fan measuring significantly larger (i.e., about 15 inches by about 15 inches). Such a significant reduction in size is very advantageous when employing such a system in tight spaces. Such systems are significantly smaller, more efficient, less expensive to manufacture (e.g., about 30% of the cost), and more robust.

An alternative configuration of a secondary metallic encasing member is shown in FIGS. 6A-6B in which tubing 612″ enters secondary block 618′ at 616′, is looped through interior of block 618′, and then exits at 616″. Although exiting at 616″, the tube is not immediately routed to a compressor and back into the first block (e.g., 518), but rather is wrapped around the exterior of secondary block 618′, providing additional heat transfer to cool the coolant within line 612″. Wrapping around block 618′, as illustrated is just one example of configurations employing this principle in which additional heat transfer is achieved by contacting (or nearly so—i.e., within about 12 inch) the tube 612″ with the exterior surface of block 618′. For example, alternatively the exterior portion of tube 612″ may zig zag up and down or similarly along one surface of the block 618′, rather than wrapping around, although wrapping may be preferred as it provides contact or close proximity between the block 618′ and the tube 612″ over significantly more of the exterior surface of block 618′. In addition, although illustrated as only wrapping around perhaps ⅔ of the overall height of block 618′ for clarity, the wrapping may cover more or less than shown.

Such heat exchanger devices may be employed in numerous heat transfer uses, for example, vehicle radiators, water heaters, air conditioners, refrigerators, personal comfort systems, swimming pool heaters, coffee pot heaters, water heaters for dishwashers, etc.

The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope. 

1. A heat exchanger apparatus comprising: at least one hollow product fluid line having an inlet at a first end, an outlet at an opposite second end, and a heat transfer portion disposed therebetween, the at least one hollow product fluid line being configured to allow passage of a fluid to be heated or cooled between the inlet and the outlet; and a metallic encasing body that encases at least a portion of the heat transfer portion of the at least one product line.
 2. A heat exchanger as recited in claim 1, wherein the metallic encasing body comprises aluminum or an aluminum alloy.
 3. A heat exchanger as recited in claim 1, wherein the metallic encasing body encases substantially all of the heat transfer portion of the at least one hollow line.
 4. A heat exchanger as recited in claim 1, wherein the metallic encasing body is formed by casting molten metal around the product fluid line.
 5. A heat exchanger as recited in claim 1, wherein the product fluid line comprises stainless steel.
 6. A heat exchanger as recited in claim 1, further comprising a second fluid line encased within said metallic body, said second fluid line being configured to convey a heating or cooling fluid, said second fluid line being in heat exchange relationship with said at least one product fluid line.
 7. A heat exchanger as recited in claim 1, wherein said metallic body further includes a plurality of convection slots formed therein.
 8. A heat exchanger as recited in claim 1, wherein the product fluid line is completely encased by said metallic body.
 9. A heat exchanger apparatus comprising: at least one hollow product fluid line having an inlet at one end, an outlet at an opposite second end, and a heat transfer portion disposed therebetween, the at least one product fluid line being configured to allow passage of a fluid to be heated or cooled between the inlet and the outlet; a second fluid line having an inlet at one end and an outlet at an opposite second end, a heat transfer portion being disposed therebetween, the second fluid line separate from said product fluid line, said second fluid line being configured to convey a heating or cooling fluid, said second fluid line being in heat exchange relationship with said product fluid line so as to heat or cool product within said product fluid line; and a metallic encasing body that encases at least a portion of each heat transfer portion of both the product fluid line and the second fluid line.
 10. A heat exchanger as recited in claim 9, wherein said metallic body further includes a plurality of convection slots formed therein.
 11. A heat exchanger as recited in claim 9, wherein the metallic encasing body comprises aluminum or an aluminum alloy.
 12. A heat exchanger as recited in claim 9, wherein the metallic encasing body encases substantially all of the heat transfer portion of the at least one hollow line.
 13. A heat exchanger as recited in claim 9, wherein the metallic encasing body is formed by casting molten metal around the product fluid line.
 14. A heat exchanger as recited in claim 9, wherein the product fluid line comprises a material different from the metallic encasing body.
 15. A heat exchanger as recited in claim 14, wherein the product fluid line comprises stainless steel.
 16. A heat exchanger system comprising: at least one hollow product fluid line having an inlet at a first end, an outlet at an opposite second end, and a heat transfer portion disposed therebetween, the at least one product fluid line being configured to allow passage of a fluid to be heated or cooled between the inlet and the outlet; and a second fluid line having an inlet at one end and an outlet at an opposite second end, a heat transfer portion being disposed therebetween, the second fluid line separate from said product fluid line, said second fluid line being configured to convey a heating or cooling fluid, said second fluid line being in heat exchange relationship with said product fluid line so as to heat or cool product within said product fluid line; a first metallic encasing body that encases at least a portion of each heat transfer portion of both the product fluid line and the second fluid line; and a second metallic encasing body separate from the first metallic encasing body that encases a subsequent portion of the second fluid line after the second fluid line exits from the first metallic encasing body.
 17. A heat exchanger system as recited in claim 16, wherein the second metallic encasing body is substantially cylindrical with a centrally disposed through hole, further comprising a housing that encloses around the sides of said cylindrical encasing body with a continuous space defined around the entire exterior of the cylindrical encasing body such that convention air may be pulled through the central through hole as well as the space between the housing and the exterior of the cylindrical body so as to convention cool the cylindrical body.
 18. A heat exchanger apparatus comprising: at least one electrically resistive heating line having a first end, an opposite second end, and a heat transfer portion disposed therebetween; and an aluminum encasing body that encases substantially all of the heat transfer portion of the electrically resistive heating line so as to facilitate heating of a fluid in contact with said aluminum encasing body. 